1. Field of the Invention
The present invention relates to the construction and maintenance of pipelines, and, more particularly, to the method of coating the internal surface of a pipeline with a cement-sand-mortar and a device for effecting same.
2. DESCRIPTION OF THE PRIOR ART
Today, there are known in the art the method and device for coating the internal surface of pipelines with a cement-sand mortar (cf. e.g., a booklet by the U.S. Ameron company "A Drawing Method of Restoring Pipelies". Instructions A-101 and A-102).
In accordance with this method and device a layer of mortar is applied on the internal surface of the pipeline in the following manner. A piston is installed in a pipeline with an annular clearance. Prior, the piston the pipeline is filled with a cement-sand mortar. With the aid of a rope the piston is drawn along the pipeline, the mortar is forced out into the clearance between the piston and the pipeline forming a layer. Due to viscosity this mortar is retained on the pipeline wall and once solidified, forms a protecting coating.
However, this method can be used for coating the internal surface of pipelines with up to 250 mm in diameter, because in larger dia. pipelines the formed coating is not held on the internal surface due to an insufficient paving and transverse strength of the layer.